Summary: The ?Permian to Cenozoic Houtman Sub-basin is a large, extensively faulted tectonic element of the Perth Basin located offshore on the southwestern Australian margin, containing up to 13 km of siliciclastic fluvial, deltaic and marine rocks.

Overview: The Houtman Sub-basin is a deep, north-northwest to south-southeast trending, extensively faulted tectonic element located on the continental shelf and slope in the offshore northern Perth Basin. It forms the largest structural element in the Perth Basin and extends about 700 km along-strike over an area of 52 800 square kilometres. Exploration drilling has been limited to only two wells in the southern Houtman Sub-basin, none encountering commercial hydrocarbon accumulations. The origin and structural characteristics of the Houtman Sub-basin are only well documented in its southern part where most seismic data have been acquired. Here, the Houtman Sub-basin contains a thick (>3100 m at Houtman 1), extensively faulted section of Upper Triassic to Jurassic, fluvial, deltaic and marine sedimentary rocks. Permian to Middle Triassic half-graben depocentres appear to extend along the eastern margin of the Houtman Sub-basin, suggesting that much of the Houtman Sub-basin originated during a Permian rifting event. The southern part of the Houtman Sub-basin probably formed as a westward-thickening sag basin across a hinge zone (the Houtman Hinge Zone) during the Middle Triassic to Middle Jurassic. Middle Jurassic to Early Cretaceous rifting produced numerous northeast and southwest dipping faults with up to 1800 m of throw, and some large wrench anticline structures along the western margin. Uplift and erosion during Valanginian break-up has removed much of the original synrift section from the Houtman Sub-basin. Post-break-up deposits form a westward thickening (up to ~1500 m thick) passive margin cover of predominantly carbonate rocks above the Middle Triassic to Jurassic depocentre. The Houtman Sub-basin contains potential source rocks for oil and gas in Jurassic strata (Yarragadee Formation, Cadda Formation and Cattamarra Coal Measures), and potential structural traps in extensional fault blocks and strike-slip related structures sealed by marine shales from the Middle Jurassic Cadda Formation. An interpreted palaeo-oil column and a minor gas accumulation at Houtman 1 provide evidence for a petroleum system.